• Wavelength Audio Proton Asynchronous USB DAC Review

    The recently released Wavelength Audio Proton USB DAC has received a lot of positive buzz around the industry. Now that I've spent countless hours with a Proton in a few playback systems of my own I will say the buzz is well deserved. There are quite a few reasons why the Proton is worthy of all the great attention it is getting. For starters the price of this DAC is within reach of the great majority of audiophiles. Plus, the DAC was developed from the ground up by Wavelength Audio's Gordon Rankin who is one of the brightest minds in computer audio today. However, the icing on the cake is the fact that the Proton uses Wavelength's own Streamlength Asynchronous USB code. The Proton doesn't require any software installation and is a true plug n' play 24/96 Asynchronous USB DAC. As the famous NY Yankee broadcaster Mel Allan would say, "How about that!"



     

     


    Proton Details

    The Wavelength Audio Proton is a small USB only DAC with single ended RCA analog outputs and a built-in headphone output. The Proton is a very versatile DAC but it's comfort zone is clearly on a desktop or in a suitcase traveling with a discerning listener. The Proton is not your average "travel DAC" or desktop audio component. This DAC is powered by a computer's USB output and does not require a separate power supply. If not implemented correctly this USB power can cause serious problems for a Digital to Analog converter. Fortunately Wavelength placed a lithium-ion battery in the Proton that supplies off-the-grid power for critical areas of the unit. A very neat feature of the Proton that I have not seen implemented in any other DAC is a software volume control that sets the hardware analog volume control in the Proton. To a listener volume control is all done via the computer's volume slider. A common misperception may be that this is a digital volume control. However, it's really software that controls the hardware analog volume control inside the Proton. Turn the computer's volume up and the Proton's analog volume control responds with a matching increase in volume. Note: The iTunes volume should remain at 100% while the Proton's volume is controlled by the system volume control.

    Taking the convenience of the Proton's volume control to another level can be done with the iPhone application Rowmote. Rowmote mimics the little Apple white remote control but sends the signals to the computer over a home network without the need for a direct line of sight to the computer like an infrared remote requires. I highly recommend the most up to date version of Rowmote as some much needed changes have improved the application immensely.

    The Proton supports 44.1, 48, 88.2 and 96k sample rates at a 24 bit word length. On the rear of the DAC are four LEDs that indication the active sample rate the Proton is using. This is not a bit perfect indicator, but when a 24/88.2 track is playing and the 96k indicator is illuminated there is clearly a playback misconfiguration. Certainly a nice feature to have on a DAC.

    I used the Proton frequently as a headphone amp because I found it a tad awkward using the DAC connected to my main playback system. Sennheiser HD600s and Grado RS-1 headphones work wonderfully with the Proton, but steer clear from Ultimate Ears ue11 Pro in ear monitors. The ue11s make every little noise a computer can generate very audible when used with the Proton. I exchanged emails with Gordon Rankin about this and he said, "The Ultimate ears are only 13 ohms. This is outside of the usuable area of the Proton." Again, the Sennheisers and the Grados performed very nicely with the Proton and I wouldn't hesitate to use them with a Proton in the future.

    I tried very hard to use the Proton, bypassing a preamp, connected directly to my McIntosh MC275 power amp and Avalon Acoustics loudspeakers, but the volume control scared me a bit. I really like the comfort of a physical mute button incase anything goes awry during a listening session. If for some reason I lost clock and noise was blaring through my speakers (this has happened in the past with other components) I wouldn't want to rely on any software from any operating system to save my tweeters. I did use the Proton through a preamp during the review by setting the computer's system volume around 90% and using the preamps volume control. This is certainly a viable configuration that should work for most listeners.


    What is Asynchronous Mode / Streamlength Asynchronous USB

    Adaptive Mode USB

    Currently almost all USB DACs use Adaptive Mode USB Audio. Even the latest native 24/96 USB DACs using CEntrance code like the Benchmark DAC1 HDR, the PS Audio Perfect Wave DAC, and a host of Empirical Audio products use Adaptive USB Mode. "In Adaptive mode the computer controls the audio transfer rate, and the USB device has to follow along updating the Master Clock (MCLK) every one millisecond. The USB bus runs at 12MHz, which is unrelated to the audio sample rate of any digital audio format (i.e. 44.1K requires a MCLK = 11.2896MHz). Therefore Adaptive Mode USB DACs must derive the critical master audio clock by use of a complex Frequency Synthesizer. Since the computer is handling many tasks at once, the timing of the USB audio transfers has variations. This leads to jitter in the derived clock, which means you are not getting the maximum sonic potential available from computer-based audio." (Adaptive USB description courtesy of Wavelength Audio)


    Asynchronous USB Mode

    Wavelength Audio's Streamlength Asynchronous Mode USB enables the USB DAC to control the computer. According to some experts Asynchronous Mode USB is a necessity for good D to A conversion. Asynchronous Mode works by using an ultra low jitter master clock in the DAC that controls the audio transfer rate from the computer. According to Wavelength Audio, "Jitter is reduced by a factor of greater than 100 times." Current DACs using similar Asynchronous implementations are the Ayre QB-9, which uses code licensed from Wavelength Audio, and the USB products from dCS. My guess as to why more manufacturers are not using Asynchronous USB is that the learning curve is very steep and it takes someone with the knowhow of Gordon Rankin or a company like dCS to bring this type of product to market. It literally took Gordon years to perfect his Streamlength Asynchronous USB code and it involved so much more than opening an instruction manual and following along. In fact there was no such thing as an instruction manual for this endeavor!

    All of these features and this advanced USB technology are available starting at $900 from Wavelength's network of dealers.




    Sound Quality

    All of the aforementioned intellectual property that went into the Proton's development must equate to a great sounding product right? Yes, it most certainly does give the Proton a sonic boost over much of the competition. Throughout this review period Blue Coast Records has been releasing some wonderful native 24/96 WAV downloads of live in studio recordings. I highly recommend these downloads as the music and sound quality are a real treat. The Blue Coast live acoustic recordings really brought out the best in the Proton. The mid range in these recordings matched perfectly with the Proton's strongest area of reproduction. I thought the mid range was produced very well through the Proton and this sonic quality continued throughout the review period with many other recordings including those from Boz Scaggs (But Beautiful, and Speak Low) and Elvis Costello (North, Momofuku, and Secret, Profane and Sugarcane). From the moment I clicked play on my Mac Pro music server the sound emanating from my system was 100% musical, appropriately smooth, and had a sense of timing that must be heard to comprehend. My armchair engineer's guess is that the Streamlength Asynchronous USB code of Gordon's has much to do with the special sound of this DAC. The Proton is far from the top of the Wavelength line-up and under certain conditions one can hear its shortcomings. In my opinion the Proton could use a touch more resolution in the polar regions of the scale, but at the same time leaving the fabulous mid range untouched. An album like Bolero from Reference Recordings wasn't reproduced to my liking through the Proton as I thought the very high and very low ends of the scale were a little less resolving than I prefer. As I'm sure any wise businessman or component designer would say, this is where the Wavelength Brick, Cosecant, or Crimson come into play. All three are the Proton's big brothers and have received their own critical acclaim.



    Conclusion

    An Asynchronous USB DAC as feature rich and with such intelligent design could literally be priced at two or three times the price of the Proton. In a way I consider the Proton to be the gateway drug of the Wavelength Audio USB DAC line-up. Listeners can get into the wonderful sound of the Wavelength Asynchronous USB DACs for very little money. Once they are hooked on the sound there is no turning back. Better sound can be had by upgrading further into the Wavelength line-up for those who can beg, borrow, or steal the money to upgrade. Fortunately the chances are pretty high that the Proton will satisfy most listener's appetites for great sound for the foreseeable future. Based on the sound quality, features, advanced technology, and very reasonable price the Proton is the value of the year in high-end audio and the next DAC to make the CASH List here at Computer Audiophile.




     

     

     


     
    CASH List



     

     

    Wavelength Audio Proton Front
    Wavelength Audio Proton Front
    click to enlarge


     

     

    Wavelength Audio Proton Angle
    Wavelength Audio Proton Angle
    click to enlarge


     

     

    Wavelength Audio Proton Rear
    Wavelength Audio Proton Rear


     

     

     


    Wavelength Audio Proton Audio Midi Options
    Wavelength Audio Proton Audio Midi Options
    click to enlarge


     

     

    Manufacturer: Wavelength Audio
    Product Page: Proton
    Price: $900
    Availability: Dealers

     

     


    The following information was gathered using the Apple application USB Prober. The information clearly states what mode a USB DAC is operating in, Adaptive or Asynchronous. The First sample of data was taken with a Benchmark DAC connected to a USB port. The second sample of data was taken with the Proton connected to my new MacBook Pro 13" via USB. The data clearly shows the supported sample rates and the USB mode as Asynchronous.

     

     





    Benchmark:

    Audio Class Specific Audio Data Format
    Audio Stream Format Type Desc.
    Format Type: 1 PCM
    Number Of Channels: 2 STEREO
    Sub Frame Size: 3
    Bit Resolution: 24
    Sample Frequency Type: 0x04 (Discrete)
    Sample Frequency: 44100 Hz
    Sample Frequency: 48000 Hz
    Sample Frequency: 88200 Hz
    Sample Frequency: 96000 Hz
    Endpoint 0x01 - Isochronous Output
    Address: 0x01 (OUT)
    Attributes: 0x09 (Isochronous adaptive data endpoint)
    Max Packet Size: 576
    Polling Interval: 1 ms

     

     


    Proton:
    Device Descriptor
    Descriptor Version Number: 0x0100
    Device Class: 0 (Composite)
    Device Subclass: 0
    Device Protocol: 0
    Device MaxPacketSize: 8
    Device VendorID/ProductID: 0x0451/0x1022 (Texas Instruments)
    Device Version Number: 0x0100
    Number of Configurations: 1
    Manufacturer String: 1 "Wavelength Audio,ltd"
    Product String: 2 "Proton USBDAC"
    Serial Number String: 3 "(C) 2009 Wavelengh Audio, ltd."


    Audio Stream Format Type Desc.
    Format Type: 1 PCM
    Number Of Channels: 2 STEREO
    Sub Frame Size: 3
    Bit Resolution: 24
    Sample Frequency Type: 0x04 (Discrete)
    Sample Frequency: 44100 Hz
    Sample Frequency: 48000 Hz
    Sample Frequency: 88200 Hz
    Sample Frequency: 96000 Hz

    Endpoint 0x01 - Isochronous Output
    Address: 0x01 (OUT)
    Attributes: 0x05 (Isochronous asynchronous data endpoint)
    Max Packet Size: 588
    Polling Interval: 1 ms



     

     

     

    Associated Equipment: Mac Pro, Lynx AES16e card, Kimber USB cable v1 & v2, Benchmark DAC1 PRE, Kimber Select cable, Avalon Acoustics speakers, McIntosh tube amplification, Virtual Dynamics power cables, Richard Gray's Power Company cables, Bel Canto USB Link, Devilsound DAC v2, Berkeley Audio Design Alpha DAC, Ayre QB-9 USB DAC.

     

     

     
    Comments 7 Comments
    1. flatmap's Avatar
      flatmap -
      I enjoyed your comments about your experience with the Proton. <br />
      <br />
      I've been living with this lovely little DAC for about 3 months now. I listen through headphones very often, but also via the rca outputs to either my tube preamp or directly into my amp. <br />
      <br />
      It does take a while to break in, longer than I thought, but I never had a moment's hesitation about its musical qualities. Everything I liked about it on day one just came into better balance and came to have a more effortless feeling over time.<br />
      <br />
      I'm not in a position to compare the performance of the Proton with other DACs. However it easy to pinpoint the things I like about it. For orchestral music, where the recording has this to offer, you can easily click into what the soloists are thinking and there's a considerable subtlety in the blending of the sound from the different sections. Likewise in opera recordings you get a solid feel for the stage, the position and direction of the singers and there's a satisfying balance between the orchestra and the singers. You get a lot of subtle refinement with this dac in handling the classical music soundscape.<br />
      <br />
      Perhaps the lowest bass effects (the thunder machine in Das Rheingold, deep drums sounds, etc.) are not as growlingly frightening as they can be. I've heard better on that score. However I would note that these instruments are very present in the overall mix; you don't miss them. I'm listening now to Des Knaben Wunderhorn (in the 96kHz version from HDTT) and it really sings with this set up. <br />
      <br />
      It's pretty hard for me to remain long in "critical listening mode" with the Proton plugged into my computer audio setup. Janet Baker sings about 3 notes and I'm just gone. You get a remarkable absence of any kind of noise and there's not a molecule of artificiality in the sound at all. So this is easy to listen to and, if you're like me, you'll find that hours pass by.<br />
      <br />
      I would at this point go on and on about the convenience and thoughtfulness of the design... but i think Chris has totally hit that already. Do note, however that this component can be one link of a completely battery driven system.
    1. vortecjr's Avatar
      vortecjr -
      Flatmap!
    1. riderforever's Avatar
      riderforever -
      Hi Chris, thank you for this other great review. The only criticism I can move is that - in my opinion - it relies a little bit too much on the Wavelength statements about the usb implementation. It's obvious that they consider the asynchronous usb implementation far ahead the adaptive one, but the claimed 100x reduction of jitter looks to me a real exageration.<br />
      <br />
      I'm not aware of all the subtle details of this kind of implementation, but I think that also with well designed adaptive usb impl the jitter could remain to a very low level, for example feeding a buffer.<br />
      <br />
      Is the review of the PS Audio PWD on the way? I'd be very interested in your opinion about the quality of its usb input.
    1. The Computer Audiophile's Avatar
      The Computer Audiophile -
      Hi riderforever - A review of the PWD and PWT will be done in the future. Since PS just started shipping production units yesterday (June 29th, 2009) I don't think anyone can really say how it sounds. For the last several weeks there have been updates to the unit's code in an effort to perfect the unit.
    1. Leonid Khachaturov's Avatar
      Leonid Khachaturov -
      The hype around asychronous USB converters seems rather funny to me. In fact, such converters are not that rare and don't necessarily cost a fortune - Tascam US-144 ($149) is asynchronous, as well as the very popular E-Mu 0404 USB 2.0 ($199).<br />
      <br />
      It's true, that "driver-less" converters (the ones that use the built-in USB Audio drivers) are usually adaptive and require some hardware programming to work asynchronously, but in the pro-sector, where the manufacturer usually provides custom drivers, the asynchronous approach is more common.
    1. bachrocks's Avatar
      bachrocks -
      Thanks Chris for this as well as your soooo many other really great reviews. I read all of your DAC reviews. These are invaluable. Especially, many are complemented with user comments as well as developers' comments in the forum. What a service you and your readers provide!<br />
      <br />
      I'm considering this for my VAIO FZ series laptop (as music server and CD player), NAD C325BEE amplifier, and Wharfdale Diamond 9.1 speakers in Korea. And thanks to this review, and also Flatmap's comments about classical music with the Proton, I feel several steps closer to purchasing it.
    1. Wavelength's Avatar
      Wavelength -
      riderforever,<br />
      <br />
      <cite>Hi Chris, thank you for this other great review. The only criticism I can move is that - in my opinion - it relies a little bit too much on the Wavelength statements about the usb implementation. It's obvious that they consider the asynchronous usb implementation far ahead the adaptive one, but the claimed 100x reduction of jitter looks to me a real exageration.<br />
      <br />
      Typical adaptive jitter as tested with a Wavecrest DTS on the best computer we have sitting here still yields 2838ps of Jitter on the Word Clock. It does go up even more with slower computers and different operating systems and hardware. Were as asynchronous would not vary under any of those conditions.<br />
      <br />
      Actually we have documented proof of the performance data that we claim. But really it is easy to see that in Adaptive mode you are changing the Master Clock used in the creation of all the I2S parameters and therefore in this alone you are creating jitter. Also the use of a noisy clock like a PLL multiplied clock (yea figure out how they derive a 11.2896Mhz clock from a 6MHz crystal oscillator) is going to add tons to the output jitter spectrum.<br />
      <br />
      Thanks<br />
      Gordon